Method for production of diaminodiphenylmethanes

ABSTRACT

The present invention concerns a process for the production of methylenedianiline (MDA) having a high monomer content.

BACKGROUND OF THE INVENTION

The present invention concerns a process for the production ofmethylenedianiline (MDA) with a high monomer content and low orthocontent by rearrangement of a condensation product (known as aminal orN,N-diphenylmethylenediamine) from aniline and formaline or anothersuitable methylene group-supplying agent such as trioxan orp-formaldehyde, catalysed on solid acids.

MDA (particularly the 4,4′-isomer) is an extremely suitable startingmaterial from which—optionally after further purification—diisocyanatesthat represent an important raw product for polyurethane systems, forexample, can be obtained by phosgenation. At the same time, thealiphatic systems that are obtained from MDA by hydrogenation of thearomatic ring also play an important role as paint resins.

Of the many conceivable methods described in the literature for theproduction of MDA, manufacture from the aniline-formaldehydecondensation product (known as aminal) is the most important because itis the most economically advantageous. Depending on the variant, thecondensation product is produced first and then rearranged in thepresence of (mostly) mineral acids such as HCl or alternatively thecondensation itself is performed in the presence of acids underrearrangement conditions.

The disadvantages of such methods in regard to the synthesis ofmonomeric MDA can be summarised as follows: depending on the reactionconditions, the methods lead to mixtures consisting of excess aniline,MDA monomer (2,2′-, 2,4′- and 4,4′-isomeric) and polynuclear compounds(known as polymer bases), from which the monomeric MDA—optionally afterconversion to the corresponding isocyanates—can be obtained. Apreparation consisting of almost polymer-free MDA bases can be obtainedonly with extreme excesses of aniline in comparison to the methylenegroup-supplying agent, leading to low space-time yields and largecirculating flows of aniline.

A further disadvantage of the preparation by catalysis of mineral acidsis the accumulation of salt-containing waste waters that occur duringneutralisation of the acid. Moreover, aqueous mineral acids lead tocorrosion problems in plants.

A whole series of suggestions for the industrial implementation of therearrangement, including the use of solid acids, has therefore alreadybeen made in order to overcome these disadvantages.

However, a feasible method for the production of MDA monomer basesavoiding mineral acids must meet the following conditions, for example:

a) Quantitative yields: an intermediate-free (aminobenzylaniline-free)product must be obtained in order to ensure that it is capable of beingphosgenated (these can be extremely troublesome in the subsequentprocessing of the MDA to MDI (phosgenation).

b) Isomer distribution: similarly to the mineral acid-catalysed method,the product composition must be able to be controlled to some extent byvarying the process parameters.

c) Service life: a catalyst used in industry must achieve an economicservice life with high space-time yields before its activity can berestored by means of regeneration.

d) Foreign substances: the catalyst used must release no tracecomponents in the product that have a negative influence on productquality. In addition, the method must cause no foreign matter, e.g. inthe form of a solvent that is foreign to the system, to be brought intothe reaction mixture.

Various attempts to obtain the pure binuclear molecule selectively havealready been described, whereby a distinction has to be made between (a)methods for the material separation of mixtures of isomers andhomologues and (b) the selective synthesis of the binuclear compounds:

(a) Methods for selective 4,4′-MDA crystallisation from halogenatedsolvents were described for example in U.S. Pat. No. 4,172,847. Thedisadvantage of this process, however, is that a foreign solvent has tobe used in a complex additional process step, as a result of whichadditional material cycles and separating operations are required.

(b) U.S. Pat. No. 4,011,278 reports on numerous conversions of polarorganic compounds using ZSM-5 zeolites and other zeolite types. It alsomentions the conversion of N-alkylaniline with formaldehyde in thepresence of zeolitic catalysts, without making any reference to reactionconditions, yields and selectivities, however.

It is known from DE-A-2 202 500 that if aminal is rearranged usingamorphous silicon-aluminium-mixed oxide cracking catalysts, high yieldsof 4,4′-isomers are obtained if the reaction is itself performed in thepresence of ortho isomers (obtained from another batch, for example). Noadditional proportions of 2,2′- and 2,4′-MDA are obtained in thepresence of these isomers, since after their primary formation theypreferentially react to higher-functional oligomeric MDA grades. A highproportion of polymer bases is therefore conventionally obtained, whichhave to be separated off from the desired 4,4′-isomer. Furthermore, thisprocess requires the o-isomers formed to be recycled as an additionalstep.

It would be more advantageous to establish conditions during the actualsynthesis of MDA that ensure high proportions of 4,4′-MDA, whereby theabove-mentioned problems of salts and corrosion can be circumvented atthe same time by synthesis using solid acids.

Thus it has already become known from the above-mentioned U.S. Pat. No.4,011,278 that high selectivities in terms of the binuclear compound andparticularly of 4,4′-MDA can sometimes be obtained using solid oxidicacids, for example, but particularly using zeolites.

EP-A-0 264 744 describes the condensation of aniline with trioxan orfree formaldehyde and the rearrangement to MDA bases using solidboron-containing zeolites. Simultaneous condensation and rearrangementas well as isolation of aminobenzylanilines with subsequentrearrangement to MDA were both performed. Although high monomerselectivities were obtained by rearrangement of the aminobenzylanilinesto MDA (approx. 90 mol % binuclear isomers in the aniline-free mixture),a complete conversion was not achieved and furthermore the reaction ispreferably performed in benzene as solvent.

Attempts have also already been made to perform the rearrangement ofaminal via aminobenzylaniline to MDA according to the prior art inseveral steps, for example in two steps, using solid acids in more thanone step. U.S. Pat. No. 4,039,581 describes the rearrangement of anaminal from formaldehyde and aniline using solid acids, whereby it isfirst dried and then rearranged using zeolites, for example, in severalreaction stages—characterised by temperature stages. A temperature of100° C. is not exceeded, however, since it is assumed that hightemperatures in the presence of water would be damaging to selectivity.A full rearrangement of the amino-benzylaniline intermediates to the MDAbases cannot be achieved under these conditions. An MDA with a binuclearcontent of approx. 90 mol % in the aniline-free mixture is obtained asproduct.

EP-A-0 329 367 describes the rearrangement of a dried aminal usingzeolitic catalysts for the purpose of selective production of binuclearMDA. An aminal is rearranged isothermally at 120° C. using dealuminisedHY zeolites and fluorinated derivatives thereof to a blend of MDA, whichalthough consisting of approx. 94 mol % (relative to aniline-freesolution) of binuclear MDA is characterised by incomplete conversion ofthe intermediates to the MDA bases. Approx. 5 mol % polymer bases areadditionally formed.

SUMMARY OF THE INVENTION

The object of the present invention was therefore to find a process bywhich, contrary to the opinion represented in the literature, theconversion of aminal to low-polymer binuclear MDA can be performed usingsolid acid catalysts and thereby to utilise the advantages of catalysiswith solids with sufficiently long catalyst residence times such as arerequired for industrial processes, without obtaining significantresidual quantities of polymeric MDA bases or incompletely rearrangedintermediates (aminobenzylanilines) in the end product.

This object is achieved according to the invention by a process for theproduction of methylenedianilines by the rearrangement of a condensationproduct consisting of aniline and a methylene group-supplying agent,e.g. formaldehyde, wherein a dried condensate of aniline and themethylene group-supplying agent having a molar ratio of aniline tomethylene group-supplying agent of 1.7 to 100 is reacted under gentleconditions in the presence of solid, acid catalysts to low-polymermethylenedianiline with a predominant content of 4,4′-isomer,characterised in that aniline is used that is largely free fromaliphatic amines.

Low-polymer methylenedianiline in the sense of the invention consists ofat least 80 wt. %, preferably 85 wt. %, particularly preferably at least90 wt. %, of binuclear compounds, of which the ortho isomer contentmakes up a maximum of 20 wt. %, preferably a maximum of 18 wt. %,particularly preferably a maximum of 16 wt. % and the content of4,4′-isomers is a minimum of 80 wt. %, preferably a minimum of 82 wt. %,particularly preferably a minimum of 84 wt. %.

It follows from this that the content of 4,4′-isomers in theaniline-free overall mixture is between 64 and 100 wt. %. This is thedefinition of the predominant content of 4,4′-isomer in the low-polymermethylenedianiline.

This process can be illustrated in idealised form by means of thefollowing diagram:

Examples of methylene group-supplying compounds in the sense of theinvention include, in addition to aqueous formaldehyde solution,p-formaldehyde and trioxan. These are reacted with aniline, whereby acondensation product is formed that can be given the alternative name ofaminal and consists predominantly of N,N-diphenylmethylenediamine. Thiscondensation product is first dehydrated before the further reaction isperformed under catalysis.

In principle the reaction to aminal can also be performed in thepresence of a catalyst that causes the rearrangement to ABA and/or theMDA isomers. However, the water that is released during the condensationreaction reduces the activity and selectivity of the catalyst, as aconsequence of which the successive version (aminalreaction→dehydration→rearrangement) is preferred.

The aminal reaction is preferably performed continuously by meteringaniline and formaldehyde solution in a molar ratio of aniline toformaldehyde of 1.7 to 100, preferably 2 to 50, particularly preferably4 to 20, into a reactor, from which a reaction quantity of the samevolume as the feed stream is continuously removed and sent for phaseseparation. A batchwise or semi-continuous process is also conceivable,whereby the aniline and formaline are metered in the desired mixingratio into a stirred batch reactor, from which the aminal that isreacted out is then sent for drying.

Dehydration can be performed both over dehydrating agents conventionallyused in industry (e.g. molecular sieve), either continuously orbatchwise, or azeotropically, for example, by means of continuous orbatchwise distillation (dehydration with the aid of the aniline alreadypresent in the system). The aniline that may optionally be drawn offduring the course of the process can conveniently be added in excessright at the beginning of the aminal reaction in order to obtain thedesired ratio of aniline to aminal after drying by distillation.

The desired ratio of aniline to formaldehyde (A/F) for the rearrangementcan be set at the time of the aminal reaction, optionally taking thedrying losses into consideration. In principle, however, it is alsopossible to perform the aminal reaction and aminal dehydration at a lowmolar A/F of 1 to 5 and then to set the desired value of 4 to 20immediately before the rearrangement using pure, dry aniline. The latteroption allows the use of smaller apparatus at the aminal reaction anddrying stages, leading to lower investment costs. Aniline recovered fromreprocessing of the reaction mixture (recycled aniline) can also be usedfor restocking after condensation, which in the case of the operationusing an excess of aniline is recovered from the fully rearranged MDA.

Drying by distillation is preferably performed continuously and underreduced pressure in order to subject the condensation product to thelowest possible thermal stress.

Dehydration is preferably performed down to a content of less than 1000ppm water, particularly preferably less than 500 ppm water.

The catalysed rearrangement of the condensation product (aminal) mustlead entirely to the desired MDA. Complete conversion is deemed to havebeen achieved when the intermediates have been reacted off down to aresidual concentration of 0 to <500 mg/kg, preferably <200 mg/kg, ofABA.

Since the secondary products (in other words, different isomercompositions) of MDA are used in various applications, flexibility inthe isomer composition is particularly important for industrial use. Theisomer composition is substantially controlled by varying the reactiontemperature and the catalyst type.

A distinction is therefore made between the first reaction phase (a),which governs selectivity, and the phase that serves to complete theconversion (b), whereby with the selected catalyst type the ratio of thetemperature in the reaction phases determines the final composition inrespect of o- and p-isomer contents. The lower the temperature in phase(a) that is selected between 0 and 70° C., the higher the content ofp-isomers that can be achieved. Conversely, high temperatures in phase(a) of between 70 and 200° C. lead to high contents of o-isomers in thereaction mixture.

In the second reaction phase (b) the temperature is adjusted to anelevated level, preferably 100 to 200° C., in order to terminate thereaction completely and to break down the intermediates.

The catalysts used according to the invention must meet the followingrequirements:

Inorganic, preferably oxidic, particularly preferably siliceouscatalysts are used.

Thus, for example, a commercially available Y-type zeolite (Faujasit)with a modulus (SiO₂/Al₂O₃) of 5 to 200 is used as catalyst, to which abinder (e.g. aluminium oxide) can be added for the purposes of moulding.The catalysts are preferably in the H⁺ form. This can optionally beachieved by known methods (acid treatment, ammonium ion exchangefollowed by heat treatment).

The catalysts can in principle be used both in powder form and in lumpform, whereby the conventional industrial processes of tabletting,pelletising or extrusion, for example, can be used for moulding,optionally with the aid of moulding additives. For industrial use in thecontinuous process, the catalyst is preferably used after moulding torun solid catalyst beds. In batchwise operation the catalysts arepreferably used in quantities of 0.1 to 1000 wt. % relative to thecatalyst-free reaction mixture, in continuous operation preferably inquantities of 0.01 to 100 kg catalyst/(kg aminal·h) especiallypreferably in quantities of 0.1-10 kg catalyst/(kg aminal·h).

Different grades and geometries, etc. of catalysts can also be usedduring the course of the process.

The process according to the invention is preferably performed in theabsence of solvents.

It has also been found that suitable inorganic catalysts, such aszeolitic catalysts for example, can be severely deactivated by theproportions of aliphatic amines contained in the aniline. For example,technical aniline contains considerable proportions of these by-products(e.g. cyclohexylamine, dicyclohexylamine), which already lead to asignificant deactivation. Technical aniline is obtained in industry bydistillation of crude aniline.

For the process according to the invention, aniline grades are thereforepreferably used that are largely free from aliphatic amines as minor andtrace constituents (e.g. cyclohexylamine, dicyclohexylamine). For theprocess according to the invention, aniline with a purity of ≧99.5 % ispreferably used, whereby aniline grades with aliphatic amine contents(e.g. cyclohexylamine, dicyclohexylamine) of less than 100 ppm arepreferred. Aniline grades with aliphatic amine contents of 0 to <25 ppmare particularly preferably used. Aliphatic amines can advantageously beremoved from aniline by adsorption, preferably chemisorption, or acidwashing.

The rearrangement according to the invention is performed with the driedaminal in such a way, for example, that the product obtained from dryingis brought into contact with the solid catalyst in suspension. Therearrangement can be performed batchwise or continuously in astirred-tank reactor, a series of stirred-tank reactors, in a tubularreactor (e.g. fixed-bed or fluidised-bed reactor) or in a combinationthereof. Serial fixed catalyst beds are advantageously used. A mixtureof aminobenzylanilines, aniline and small quantities ofdiaminophenylmethanes is first obtained in a temperature range of 20 to70° C., preferably 40 to 60° C., depending on the catalyst used. To thisend, the reaction mixture is preferably pumped over the fixed catalystbed, whereby residence times of 0.2 to 2 hours are typically set. Theoptimum temperature for a selected catalyst and a desired isomer ratioin the aminobenzylanilines obtained is easily determined by means ofpreliminary tests.

In the continuing process the further rearrangement of theaminobenzylanilines to the MDA isomers is performed at an increasedtemperature of 70 to 140° C., preferably 90 to 130° C., wherebyresidence times of 0.2 to 2 hours are typically set. In this case too acatalyst bed is used as the particularly preferred embodiment, althoughall other above-mentioned methods can also be used.

In the continuing process the rearrangement of any residualaminobenzylanilines to MDA isomers can if necessary be performed at afurther increased temperature of 130 to 200° C., preferably 140 to 175°C., without MDA polymers being formed in significant quantities orconsiderable quantities of 4,4′-MDA being isomerised to ortho isomers.To this end, residence times of 0.02 to 2 hours, preferably 0.1 to 1hour, are typically set in an additional catalyst bed.

On completion of the reaction, the reaction mixture obtained by theprocess according to the invention can be processed in a step (c) suchthat the excess aniline optionally contained in the mixture can beseparated from the MDA isomers either continuously or batchwise by knownmethods such as distillation or crystallisation, for example, andrecycled. The MDA isomers are then sent for subsequent phosgenation.

It is surprising that low-polymer MDA grades with a high proportion of4,4′-isomer can be obtained by this process and that commercial Yzeolites can be used as catalysts for this process without their firsthaving to undergo a modification, e.g. fluorination. It is particularlysurprising that by varying the temperature and/or the catalyst type inthe first reaction phase (a), the p-isomer content can be selectivelycontrolled and the o-isomer content (2,4′-MDA and 2,2′-MDA) minimised toa maximum of 20 wt. %, preferably a maximum of 18 wt. %, particularlypreferably a maximum of 16 wt. % (relative to the total quantity ofbinuclear compounds).

The product properties obtained by the process according to theinvention are adjusted by combining the process parameters oftemperature, A/F ratio, and particularly by choosing the zeolite withthe optimum activity in the selected temperature window, as shown in thefollowing examples.

The present invention is illustrated by means of the following examples,but is in no way restricted to these examples. The examples are intendedin particular to help the person skilled in the art to select suitablecatalysts for the desired version of the process and to determine theoptimum temperature progression for a selected catalyst.

EXAMPLES Example 1

300 g aniline and 33.6 g aqueous formaldehyde solution (32 wt. %formaldehyde in water) corresponding to a molar ratio of A/F=9 areplaced together in a batch reactor under protective gas, whereby at atemperature of 60° C. the formation of aminal is initiated spontaneouslyand without catalysis. After the reaction mixture is transferred to aseparating funnel, phase separation begins and the organic phase isseparated off and subjected to an additional drying.

This drying was performed in various ways, whereby the selected methodhad no significant influence on the final result:

a) by means of drying agents:

50 g of a dry zeolite (molecular sieve 4 Å, Bayer AG) is added to themoist aminal phase (170 g) at approx. 60-80° C. and the solutionstanding above the molecular sieve is stirred for approx. 1 h. Theorganic phase dried in this way is clear and light brown in colour andhas an average water content determined by the Karl Fischer method of<0.05%.

b) by means of batch distillation:

The aqueous aminal emulsion (527.5 g) with a water content of approx. 5wt. % is dehydrated by batchwise distillation through a water separatorunder reflux in a 1000 ml flask at a pressure of 100 hPa. Distillationis initially performed at an overhead temperature of approx. 50° C.which, as the water concentration in the aminal falls, must be increasedto a maximum overhead temperature of 110 to 115° C. with a bottomstemperature of 117 to 120° C. In the water separator the water andaniline phase of the condensate are separated and the aniline phasereturned to the flask. An average water content of approx. 0.04 % wasdetermined in the clear, pale-brown solution from the bottoms (460 g)according to the Karl Fischer method.

c) by means of continuous distillation:

The aqueous aminal emulsion with a water content of approx. 5 wt. % isdehydrated by continuous distillation in a rectifying column. The moistaminal from the column at an overhead pressure of 100 mbar, for example,and a corresponding overhead temperature of 48° C. is supplied as feedat 100 g/h such that a water-aniline azeotrope can be continuouslyremoved from the top at 18 g/h and the practically anhydrous aminalremoved from the foot at 82 g/h. An average water content of approx.0.04% was determined in the clear, pale-brown withdrawal from thebottoms according to the Karl Fischer method.

Example 2

a) The aminal produced and dried according to example 1 a) is reacted ina discontinuous experimental arrangement with a commercial H—Y zeoliteextrudate (DEGUSSA WESSALITH® DAY F 20, Degussa AG) activated at 300° C.for 15 h. 15 g of the activated moulded catalyst is used for 100 g dryaminal. The reaction is then performed in a temperature-graduatedoperation at 50° C. for 6 h and then at 130° C. for 4 h and the reactionmixture analysed by HPLC. The final intermediate residues(aminobenzylanilines) are depleted in the high-temperature phase withinthe analytical detection limit. An MDA having a composition of 98 mol %monomeric MDA and 2 mol % polynuclear compounds relative to theaniline-free mixture is obtained. The o-isomer content is 14 mol %.

b) Similarly to example 2 A), the same quantities are reacted undercomparable apparatus conditions, except that the temperature is notgraduated and the reaction is instead performed isothermally at 130° C.After the final intermediate residues (aminobenzylanilines) havedepleted completely within the analytical detection limit, an MDA havinga composition of 91 mol % monomeric MDA and 9 mol % polynuclearcompounds relative to the aniline-free mixture is obtained. The o-isomercontent is 21 mol %.

Example 3

The aminal produced and dried according to example 1 a) is reacted in aforced circulation experiment with a commercial H—Y zeolite extrudate(WESSALITH® DAY F 20, Degussa AG) that has previously been activated at300° C. for 15 h. The dry aminal is passed over a bed of the activatedcatalyst, which is contained in a jacket-heated glass tube. In a firstreactor the aminal is passed over the fixed bed consisting of 50 gcatalyst at 50° C. and at a volumetric flow rate of approx. 60 ml/minand pumped back into the reactor, achieving a total running time of 90min. In an identical reactor the reaction mixture is then pumped overthe catalyst bed at 130° C. for 45 min. The final conditioning isperformed at 150° C. for a further 30 min in an identical structure,whereby this final phase is intended purely as a security measure toensure the complete depletion of the undesirable aminobenzylanilineintermediates. The final intermediate residues (aminobenzylanilines) areagain depleted in the high-temperature phase within the analyticaldetection limit. An MDA having a composition of 97 mol % monomeric MDAand 3% polynuclear compounds is obtained. The o-isomer content is 14%.

Example 4

In the same way as in example 3, each graduation (50→130→150° C.) isperformed in succession for 20 identical reaction cycles using freshlyprepared aminal, whereby the following conversions (in % of theoreticalyield) and selectivities were observed as a function of the runningtime.

Run 3 7 13 20 4,4′-MDA: 84.1% 83.4% 84.0% 84.8% 2,4-MDA: 13.5% 12.7%12.9% 14.6%

Example 5

The aminal produced and dried according to example 1 b) is reacted witha commercial H—Y zeolite extrudate (WESSALITH® DAY F 20, Si/Al=23,Degussa AG) that has previously been activated at 300° C. for 15 h. Thedry aminal solution is passed at a mass flow rate of 180 g/h over a bedof catalyst (72 g) contained in a jacket-heated glass tube (200×30 mm).With this design of catalyst bed, only a partial rearrangement of theaminal solution used (approx. 50% of theoretical) is to be expectedbelow the selected reaction temperature of T=50° C. Samples of theemerging flow of material are then taken at regular intervals in orderto quantify the activity of the catalyst according to the reaction time.These are analysed in terms of conversion by means of HPLC. Thefollowing aminal conversions to the corresponding rearrangement products(aminobenzylanilines, MDA) after a catalyst service life of 24 h weredetermined according to the content of aliphatic amines in the anilineused:

Aliphatic amines (ppm) Conversion (% of theoretical) <5 62% 15 43% 6023% 1000  <1%

Example 6

As in the experiment described in example 5, several fixed beds with acatalyst bed are operated in series at increasing temperatures. The dryaminal solution is passed at a mass flow rate of 180 g/h over a seriesof three connected beds, each comprising 72 g of the catalyst WESSALITH®DAY F 20, Degussa AG, which in each case is contained in jacket-heatedglass tubes (200×30 mm) at a temperature of 50° C. The reaction mixturethen flows through a series of two fixed beds of identical design (2×72g of the same catalyst), which are operated at 130° C. Finally it ispassed through a fixed bed of the same design heated to 150° C. (72 g ofthe same catalyst). Samples of the emerging flow of material are thentaken at regular intervals in order to quantify the activity of thecatalyst according to the reaction time. These are analysed in terms ofconversion by means of HPLC.

In this way, using aniline with a cyclohexylamine content of approx. 15ppm, an MDA having a composition of 98 mol % monomeric MDA and 2 mol %polynuclear compounds relative to the aniline-free mixture is obtainedunchanged over a continuous total operating period of 5 days. Theo-isomer content is 10 mol %.

What is claimed is:
 1. A process for the production ofmethylenedianilines comprising (1) condensing aniline which containsless than 100 ppm aliphatic amines, and a methylene group-supplyingagent, at a molar ratio of aniline to methylene group-supplying agent of1.7:1 to 100:1 to form a condensate of aniline and the methylenegroup-supplying agent; (2) drying the condensate of aniline and themethylene group-supplying agent; and (3) rearranging the driedcondensate under gentle conditions in the presence of solid, inorganic,acid catalysts to form low-polymer methylenedianiline with a predominant4,4′-isomer content.
 2. The process according to claim 1, wherein saidrearranging of the dried condensate is performed in at least two stagesat a temperature that increases between the stages.
 3. The processaccording to claim 1, wherein said aniline contains less than 25 ppmaliphatic amines.
 4. The process according to claim 1, wherein thecatalysts are selected from the group consisting of powdered zeolitesand zeolite mouldings in the H⁺ form, which are present in suspension oras fixed beds.
 5. The process according to claim 1, wherein saidrearranging is performed batchwise in a stirred-tank reactor,continuously in a stirred-tank reactor, in a series of stirred-tankreactors, in a tubular reactor, in a fixed-bed reactor, in afluidized-bed reactor or in a combination thereof.
 6. The processaccording to claim 1, wherein the condensate of aniline and themethylene group-supplying agent comprises an aminal or a solutionthereof that contains less than 1000 ppm water.
 7. The process accordingto claim 1, wherein said catalysts comprise FAU zeolites.